JP2018096556A - Material gas liquefaction device and its control method - Google Patents

Material gas liquefaction device and its control method Download PDF

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Publication number
JP2018096556A
JP2018096556A JP2016238535A JP2016238535A JP2018096556A JP 2018096556 A JP2018096556 A JP 2018096556A JP 2016238535 A JP2016238535 A JP 2016238535A JP 2016238535 A JP2016238535 A JP 2016238535A JP 2018096556 A JP2018096556 A JP 2018096556A
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Prior art keywords
expander
pressure
low
rotational speed
control
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Inventor
直隆 山添
Naotaka Yamazoe
直隆 山添
智浩 阪本
Tomohiro Sakamoto
智浩 阪本
英隆 宮崎
Hidetaka Miyazaki
英隆 宮崎
大祐 仮屋
Daisuke Kariya
大祐 仮屋
三輪 靖雄
Yasuo Miwa
靖雄 三輪
雄一 齋藤
Yuichi Saito
雄一 齋藤
木村 洋介
Yosuke Kimura
洋介 木村
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川崎重工業株式会社
Kawasaki Heavy Ind Ltd
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Priority to JP2016238535A priority Critical patent/JP2018096556A/en
Publication of JP2018096556A publication Critical patent/JP2018096556A/en
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01DNON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D17/00Regulating or controlling by varying flow
    • F01D17/02Arrangement of sensing elements
    • F01D17/06Arrangement of sensing elements responsive to speed
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT-PUMP SYSTEMS
    • F25B1/00Compression machines, plant, or systems with non-reversible cycle
    • F25B1/10Compression machines, plant, or systems with non-reversible cycle with multi-stage compression
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT-PUMP SYSTEMS
    • F25B9/00Compression machines, plant, or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/06Compression machines, plant, or systems, in which the refrigerant is air or other gas of low boiling point using expanders
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/0002Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the fluid to be liquefied
    • F25J1/0005Light or noble gases
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/0002Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the fluid to be liquefied
    • F25J1/0005Light or noble gases
    • F25J1/0007Helium
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    • F25J1/0002Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the fluid to be liquefied
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    • F25J1/001Hydrogen
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    • F25J1/003Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
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    • F25J1/005Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle by expansion of a gaseous refrigerant stream with extraction of work
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    • F25J1/0052Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle by vaporising a liquid refrigerant stream
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    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
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    • F25J1/0067Hydrogen
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    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0203Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a single-component refrigerant [SCR] fluid in a closed vapor compression cycle
    • F25J1/0204Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a single-component refrigerant [SCR] fluid in a closed vapor compression cycle as a single flow SCR cycle
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
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    • F25J1/0221Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using the cold stored in an external cryogenic component in an open refrigeration loop
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    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
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    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
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    • F25J1/0244Operation; Control and regulation; Instrumentation
    • F25J1/0245Different modes, i.e. 'runs', of operation; Process control
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    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0244Operation; Control and regulation; Instrumentation
    • F25J1/0245Different modes, i.e. 'runs', of operation; Process control
    • F25J1/0248Stopping of the process, e.g. defrosting or deriming, maintenance; Back-up mode or systems
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01KSTEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
    • F01K25/00Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for
    • F01K25/08Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for using special vapours
    • F01K25/10Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for using special vapours the vapours being cold, e.g. ammonia, carbon dioxide, ether
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT-PUMP SYSTEMS
    • F25B2600/00Control issues
    • F25B2600/25Control of valves
    • F25B2600/2513Expansion valves
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    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
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    • F25J2210/42Nitrogen
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    • F25J2240/02Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream
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    • F25J2240/40Expansion without extracting work, i.e. isenthalpic throttling, e.g. JT valve, regulating valve or venturi, or isentropic nozzle, e.g. Laval
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    • F25J2270/00Refrigeration techniques used
    • F25J2270/14External refrigeration with work-producing gas expansion loop
    • F25J2270/16External refrigeration with work-producing gas expansion loop with mutliple gas expansion loops of the same refrigerant

Abstract

PROBLEM TO BE SOLVED: To prevent a rotating speed of an expander from rushing into a critical speed range without schedule in starting and stopping the expander, even when an operation characteristic of the expander changes in a material gas liquefaction device.SOLUTION: A material gas liquefaction device includes a feed line for supplying a material gas, a refrigerant circulation line having a turbine-type expander generating cold heat by expanding a refrigerant to cool a material gas and an expander inlet valve disposed at an inlet side of the expander, and circulating the refrigerant, a heat exchanger for exchanging heat between the material gas and the refrigerant, a cooler for initial cooling of the material gas and the refrigerant by heat exchange with liquid nitrogen, and a control device performing feedback control to make a rotating speed of the expander agree with a prescribed target value by controlling an opening of the expander inlet valve in starting and stopping the expander.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a raw material gas liquefying apparatus for liquefying a raw material gas liquefied at an extremely low temperature such as hydrogen gas and a control method therefor.

  Conventionally, for example, a raw material gas liquefying apparatus for liquefying a raw material gas liquefied at an extremely low temperature such as hydrogen gas is known. Patent Document 1 discloses this type of technology.

  The raw material gas liquefying apparatus of Patent Document 1 was devised by the inventors of the present application, and corresponds to the prior art of the present invention. The raw material gas liquefying apparatus includes a feed line through which a raw material gas to be liquefied passes, a refrigerant circulation line for circulating a refrigerant for cooling the raw material gas, a heat exchanger that performs heat exchange between the raw material gas and the refrigerant, and liquid nitrogen And a cooler that performs initial cooling of the raw material gas and the refrigerant by heat exchange. Here, the refrigerant circulation line is provided with a compressor, a turbine-type expander (expansion turbine), an expander inlet valve that adjusts the flow rate of the refrigerant flowing into the expander, and an expander bypass valve that bypasses the expander. ing. The refrigerant circulating in the refrigerant circulation line is compressed by the compressor, adiabatically expanded by the expander, cooled, and heated by heat exchange with the raw material gas by the heat exchanger, and returned to the compressor.

  In the raw material gas liquefying apparatus of Patent Document 1 described above, a gas bearing unit is employed for the rotor bearing of the expander. Before starting the expander, the initially cooled refrigerant is flowed to the gas bearing unit, Perform initial cooling.

  Further, in the raw material gas liquefying apparatus of Patent Document 1, the load on the heat exchanger is reduced by changing the opening of the expander inlet valve and the expander bypass valve based on a preset valve opening schedule. The expansion machine is started and stopped while reducing the shaft vibration of the expansion machine.

JP 2006-183827 A

  In general, the operation characteristics (rotation start / stop characteristics) of an expander vary from operation to operation due to deterioration of equipment over time, adhesion of impurities contained in source gas or refrigerant to a bearing, and the like. However, in the raw material gas liquefaction device of Patent Document 1, the opening degree of the expander inlet valve and the expander bypass valve changes according to the valve opening schedule, but the operating characteristics are affected by the change in the rotation speed of the expander. Changes are not taken into account. In this respect, there is still room for improvement in the technique of Patent Document 1.

A raw material gas liquefaction apparatus according to one aspect of the present invention is provided.
A feed line for supplying a raw material gas whose boiling point is lower than that of nitrogen gas;
A refrigerant circulation line through which a refrigerant for cooling the raw material gas circulates, and expands the refrigerant to generate cold heat, and an expander inlet provided on the inlet side of the expander A refrigerant circulation line having a valve;
A heat exchanger in which heat exchange is performed between the source gas and the refrigerant;
A cooler that performs initial cooling of the source gas and the refrigerant by heat exchange with liquid nitrogen;
An expander rotation speed sensor for detecting the rotation speed of the expander;
When the expander is started and stopped, an opening degree command for the expander inlet valve is generated by feedback control that matches the rotation speed of the expander with a predetermined target value. And a control device that outputs to the valve.

Moreover, the control method of the raw material gas liquefying apparatus according to one embodiment of the present invention includes:
A feed line for supplying a raw material gas whose boiling point is lower than that of nitrogen gas;
A refrigerant circulation line through which a refrigerant for cooling the raw material gas circulates, and expands the refrigerant to generate cold heat, and an expander inlet provided on the inlet side of the expander A refrigerant circulation line having a valve;
A heat exchanger in which heat exchange is performed between the source gas and the refrigerant;
A cooler that performs initial cooling of the source gas and the refrigerant by heat exchange with liquid nitrogen;
A control method of a raw material gas liquefying device comprising a control device for performing operation control on the feed line and the refrigerant circulation line,
At the time of starting and stopping of the expander, the opening degree of the expander inlet valve is operated, and feedback control is performed so that the rotation speed of the expander matches a predetermined target value.

  According to the raw material gas liquefying apparatus and the control method thereof, the rotation speed of the expander is directly controlled when the expander is started and stopped. As a result, even if the operating characteristics of the expander change, it is possible to prevent the rotation speed of the expander from entering the dangerous speed region without a plan when the expander is started and stopped. Further, by controlling the rotation speed of the expander, it is possible to quickly pass the dangerous speed region and suppress the shaft vibration of the expander. As a result, damage caused by excessive shaft vibration of the expander such as seizure of the expander bearing can be avoided.

  According to the present invention, in the raw material gas liquefaction apparatus, even if the operating characteristics of the expander change, it is possible to avoid the rotational speed of the expander from entering the dangerous speed region without a plan when the expander is started and stopped. .

FIG. 1 is a diagram showing an overall configuration of a raw material gas liquefying apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing a configuration of a control system of the raw material gas liquefying apparatus. FIG. 3 is a diagram for explaining the flow of processing for activation control. FIG. 4 is a timing chart of activation control. FIG. 5 is a diagram for explaining the flow of the stop control process. FIG. 6 is a timing chart of stop control.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an overall configuration of a source gas liquefying apparatus 100 according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration of a control system of the source gas liquefying apparatus 100. The raw material gas liquefying apparatus 100 according to the present embodiment is an apparatus that generates a liquefied raw material gas by cooling and liquefying a supplied raw material gas. In the present embodiment, high-purity hydrogen gas is used as the source gas, and as a result, liquid hydrogen is generated as the liquefied source gas. However, the source gas is not limited to hydrogen gas, and may be a substance that is a gas at normal temperature and pressure and has a boiling point lower than that of nitrogen gas (−196 ° C.). Examples of such source gas include hydrogen gas, helium gas, neon gas, and the like.

  As shown in FIGS. 1 and 2, the source gas liquefying apparatus 100 includes a feed line 1 through which source gas flows, a refrigerant circulation line 3 through which a refrigerant circulates, and a control device 6 that controls the operation of the source gas liquefying apparatus 100. I have. The raw material gas liquefying apparatus 100 is provided with a plurality of stages of heat exchangers 81 to 86 for exchanging heat between the raw material gas flowing through the feed line 1 and the refrigerant flowing through the refrigerant circulation line 3, and coolers 73 and 88. .

[Configuration of feed line 1]
The feed line 1 is a flow path through which the source gas flows, and includes a high temperature side flow path in the heat exchangers 81 to 86, a flow path in the coolers 73 and 88, a supply system Joule-Thomson valve (hereinafter referred to as “supply system JT”). Valve 16 "), and a flow path in the pipe connecting them. The feed line 1 is supplied with a normal temperature and high pressure source gas that has been pressurized by a compressor (not shown).

  The feed line 1 passes through the first stage heat exchanger 81, the initial cooler 73, the second to sixth stage heat exchangers 82 to 86, the cooler 88, and the supply system JT valve 16 in that order. . In the heat exchangers 81 to 86, heat exchange between the source gas and the refrigerant is performed, and the source gas is cooled.

  The feed line 1 passes through the initial cooler 73 before leaving the first stage heat exchanger 81 and entering the second stage heat exchanger 82. The initial cooler 73 includes a liquid nitrogen storage tank 71 that stores liquid nitrogen, and a nitrogen line 70 that supplies liquid nitrogen to the liquid nitrogen storage tank 71 from the outside. The feed line 1 is passed through the liquid nitrogen storage tank 71. ing. In the initial cooler 73, the source gas and the refrigerant are cooled to approximately the temperature of liquid nitrogen by liquid nitrogen.

  Further, the feed line 1 passes through the cooler 88 until it leaves the sixth-stage heat exchanger 86 and enters the supply system JT valve 16. The cooler 88 includes a liquefied refrigerant storage tank 40 that stores a liquefied refrigerant obtained by liquefying the refrigerant in the refrigerant circulation line 3, and the feed line 1 is passed through the liquefied refrigerant storage tank 40. In the cooler 88, the raw material gas is cooled to approximately the temperature of the liquefied refrigerant (that is, extremely low temperature) by the liquefied refrigerant in the liquefied refrigerant storage tank 40.

  As described above, the cryogenic raw material gas exiting from the cooler 88 flows into the supply system JT valve 16. In the supply system JT valve 16, the cryogenic raw material gas undergoes Joule-Thompson expansion to become a low-temperature normal-pressure liquid. The liquefied raw material gas (that is, liquefied raw material gas) is sent to a storage tank (not shown) and stored. The production amount of the liquefied raw material gas is adjusted by the opening degree of the supply system JT valve 16.

[Configuration of refrigerant circulation line 3]
The refrigerant circulation line 3 is a closed flow path through which the refrigerant circulates, and includes a flow path in the heat exchangers 81 to 86, a flow path in the cooler 73, two compressors 32 and 33, and two flow paths. It is formed by expanders 37 and 38, a circulation system Joule-Thomson valve (hereinafter referred to as “circulation system JT valve 36”), a liquefied refrigerant storage tank 40, and a flow path in a pipe connecting them. In the feed line 1 and the refrigerant circulation line 3, a portion including the first to sixth stage heat exchangers 81 to 86, the initial cooler 73, the cooler 88, and the expanders 37 and 38 is configured as the liquefier 20. Has been.

  The refrigerant circulation line 3 is connected to a charging line (not shown) for charging the refrigerant. In this embodiment, hydrogen is used as the refrigerant. However, the refrigerant is not limited to hydrogen, and may be a substance that is a gas at normal temperature and pressure and has a boiling point equal to or lower than that of the source gas. Examples of such a refrigerant include hydrogen, helium, neon, and the like.

  The refrigerant circulation line 3 has two circulation channels (closed loops) that partially share the channel of the refrigerant liquefaction route 41 and the cold heat generation route 42. The refrigerant liquefaction route 41 includes a low-pressure side compressor (hereinafter referred to as “low-pressure compressor 32”), a high-pressure side compressor (hereinafter referred to as “high-pressure compressor 33”), and a first-stage heat exchanger 81. High-temperature side refrigerant flow path, initial cooler 73, high-temperature side refrigerant flow path of second to sixth heat exchangers 82 to 86, circulation system JT valve 36, liquefied refrigerant storage tank 40, and from the sixth stage The low-temperature compressor 32 is returned to the low-temperature compressor 32 through the low-temperature side refrigerant passages of the first-stage heat exchangers 86 to 81 in order.

  A low pressure flow path 31 </ b> L is connected to the inlet of the low pressure compressor 32. The outlet of the low pressure compressor 32 and the inlet of the high pressure compressor 33 are connected by an intermediate pressure channel 31M. The refrigerant in the low pressure passage 31L is compressed by the low pressure compressor 32 and discharged to the intermediate pressure passage 31M. The outlet of the high-pressure compressor 33 and the inlet of the circulation system JT valve 36 are connected by a high-pressure channel 31H. The refrigerant in the intermediate pressure channel 31M is compressed by the high pressure compressor 33 and discharged to the high pressure channel 31H.

  The refrigerant in the high-pressure channel 31H is the high-temperature side refrigerant channel of the first-stage heat exchanger 81, the initial cooler 73, and the high-temperature side refrigerant channels of the second to sixth-stage heat exchangers 82 to 86. In that order, and flows into the circulation system JT valve 36. The refrigerant liquefied by Joule-Thompson expansion in the circulation system JT valve 36 flows into the liquefied refrigerant storage tank 40. The amount of liquefied refrigerant produced is adjusted by the opening degree of the circulation system JT valve 36.

  In the liquefied refrigerant storage tank 40 in which the liquefied refrigerant is stored, boil-off gas is generated. This boil-off gas flows into the low-pressure channel 31L that connects the outlet of the liquefied refrigerant storage tank 40 and the inlet of the low-pressure compressor 32. The low pressure channel 31L passes through the first to sixth heat exchangers 81 to 86 in the reverse order of the high pressure channel 31H. That is, the low pressure flow path 31L passes from the sixth-stage heat exchanger 86 to the first-stage heat exchanger 81 in that order. The refrigerant in the low-pressure channel 31 </ b> L is heated while passing through the low-temperature side refrigerant channel of the heat exchangers 86 to 81 and returned to the inlet of the low-pressure compressor 32.

  On the other hand, the cold heat generation route 42 is a high-pressure compressor 33, a high-temperature side refrigerant flow path of the first to second heat exchangers 81 to 82, a high-pressure side expander (hereinafter referred to as “high-pressure expander 37”). ) Low-temperature side refrigerant flow of the fourth-stage heat exchanger 84, the low-pressure side expander (hereinafter referred to as “low-pressure expander 38”), and the fifth to first-stage heat exchangers 85-81. It passes through the path in order and returns to the high-pressure compressor 33. The expanders 37 and 38 are turbine-type expanders, and provided with rotation speed sensors 56 and 57 for detecting the rotation speeds N1 and N2 of the rotor shaft of the turbine. In this specification and claims, the rotational speed of the rotor shaft of the turbine of the expanders 37 and 38 may be simply expressed as the rotational speed of the expanders 37 and 38.

  The refrigerant liquefaction route 41 and the cold heat generation route 42 share a flow path from the high-pressure compressor 33 to the second-stage heat exchanger 82. In the high-pressure channel 31H, a branch part 31d is provided between the outlet of the second-stage heat exchanger 82 and the inlet of the third-stage heat exchanger 83, and the cold heat generation channel 31C is provided in the branch part 31d. The upstream end of is connected. The downstream end of the cold heat generation flow path 31C is connected to the intermediate pressure flow path 31M.

  The cold heat generation flow path 31C includes a high-pressure expander 37, a fourth-stage heat exchanger 84, a low-pressure expander 38, and a fifth-stage to first-stage heat between the branch portion 31d and the intermediate-pressure flow path 31M. It passes through the low temperature side refrigerant flow path of the exchangers 85-81. Most of the refrigerant that has passed through the second-stage heat exchanger 82 in the high-pressure channel 31H flows to the cold heat generation channel 31C and the remainder flows to the third-stage heat exchanger 83 by the operation of the high-pressure expander 37. .

  The high-pressure refrigerant having a temperature lower than the temperature of liquid nitrogen flowing into the cold heat generation flow path 31C is lowered and lowered by expansion in the high-pressure expander 37, passes through the fourth heat exchanger 84, and then flows in the low-pressure expander 38. The pressure is further lowered and the temperature is lowered by the expansion. The cryogenic refrigerant discharged from the low-pressure expander 38 is further passed through the fifth-stage heat exchanger 85 to the first-stage heat exchanger 81 in order to increase the temperature (ie, the raw material gas and the high-pressure flow). The refrigerant in the passage 31H is cooled) and merges with the refrigerant in the intermediate pressure passage 31M.

  In the cold heat generation flow path 31 </ b> C, a high-pressure expander inlet valve 21 that adjusts the flow rate of the refrigerant flowing into the high-pressure expander 37 is provided on the inlet side of the high-pressure expander 37. On the side, a high-pressure expander inlet-side flow rate sensor 58 that detects the flow rate F1 of refrigerant flowing into the cold heat generation flow path 31C (hereinafter referred to as “high-pressure expander inlet-side flow rate F1”) is provided. In the cold heat generation passage 31C, on the outlet side of the high-pressure expander 37, a high-pressure expander outlet temperature sensor that detects the temperature of the refrigerant that has come out of the high-pressure expander 37 (hereinafter referred to as “high-pressure expander outlet temperature T1”). 51 is provided.

  Similarly, a low-pressure expander inlet valve 22 that adjusts the flow rate of the refrigerant flowing into the low-pressure expander 38 is provided on the inlet side of the low-pressure expander 38 in the cold heat generation flow path 31C. A low-pressure expander inlet-side flow rate sensor 59 for detecting the flow rate F2 of refrigerant flowing from the high-pressure expander 37 (hereinafter referred to as “low-pressure expander inlet-side flow rate F2”) is provided upstream of the high-pressure expander 37. In the cold heat generation flow path 31C, on the outlet side of the low-pressure expander 38, a low-pressure expander outlet temperature sensor that detects the temperature of the refrigerant discharged from the low-pressure expander 38 (hereinafter referred to as “low-pressure expander outlet temperature T2”). 52 is provided.

  In the cold heat generation flow path 31 </ b> C, the upstream end of the high pressure expander bypass flow path 23 is connected upstream of the high pressure expander inlet valve 21 and downstream of the flow rate sensor 53. The downstream end of the high-pressure expander bypass flow path 23 is connected to the upstream side of the heat exchanger 84 and the downstream side of the high-pressure expander outlet temperature sensor 51 in the cold heat generation flow path 31C. That is, the high-pressure expander bypass flow path 23 connects the inlet side and the outlet side of the high-pressure expander 37 and bypasses the high-pressure expander 37. The high-pressure expander bypass passage 23 is provided with a high-pressure expander bypass valve 24.

  Similarly, the upstream end of the low pressure expander bypass flow path 26 is connected to the cold heat generation flow path 31 </ b> C upstream from the low pressure expander inlet valve 22 and downstream from the heat exchanger 84. The downstream end of the low-pressure expander bypass flow path 26 is connected to the upstream side of the heat exchanger 85 and the downstream side of the low-pressure expander outlet temperature sensor 52 in the cold heat generation flow path 31C. That is, the low pressure expander bypass flow path 26 connects the inlet side and the outlet side of the low pressure expander 38 and bypasses the low pressure expander 38. The low-pressure expander bypass passage 26 is provided with a low-pressure expander bypass valve 27.

[Configuration of control system of raw material gas liquefying apparatus 100]
The control device 6 is a device that performs operation control relating to the feed line 1 and the refrigerant circulation line 3. In the present embodiment, in particular, the starting method and the stopping method of the raw material gas liquefying device 100, more specifically, the high-pressure expander 37 and the low-pressure expansion. It is an apparatus for executing the starting method and the stopping method of the machine 38. The control device 6 controls the start and stop of the high pressure expander 37 and the low pressure expander 38 while coordinating the high pressure expander 37 and the low pressure expander 38.

  The raw material gas liquefying apparatus 100 is provided with various sensors for detecting the process data, and these sensors are connected to the control apparatus 6 so as to be able to transmit detected values. For example, the control device 6 includes a high pressure expander outlet temperature sensor 51, a low pressure expander outlet temperature sensor 52, a high pressure expander rotational speed sensor 56, a low pressure expander rotational speed sensor 57, a high pressure expander inlet side flow sensor 58, and It is connected to the low-pressure expander inlet side flow rate sensor 59, and the detection value can be acquired from these sensors.

  The opening degree of each of the high-pressure expander inlet valve 21, the low-pressure expander inlet valve 22, the high-pressure expander bypass valve 24, and the low-pressure expander bypass valve 27 of the raw material gas liquefying apparatus 100 is controlled by the control device 6. Is done. The control device 6 is a so-called computer, and exhibits functions as a start control unit 61 and a stop control unit 62 by executing a program stored in advance. These functional units of the control device 6 obtain the opening degree of the valve based on the acquired process data, and output the opening degree instruction to the corresponding valve. Each valve operates to receive an opening degree command from the control device 6 and realize an opening degree corresponding to the opening degree command.

(Startup control)
First, activation control by the control device 6 will be described. FIG. 3 is a diagram for explaining the flow of activation control processing, and FIG. 4 is a timing chart of activation control. In FIG. 3, the flow of the start control of the low-pressure expander 38 is described. However, the start-up control of the low-pressure expander 38 and the start-up control of the high-pressure expander 37 have different schedules and set values used. The contents of the process are substantially the same, and the process of starting control of the high-pressure expander 37 will be described with reference to FIG. In FIG. 4, the upper chart represents the change over time of the high-pressure expander rotational speed N1, the opening degree of the high-pressure expander inlet valve 21, and the opening degree of the high-pressure expander bypass valve 24, and the lower chart represents the low-pressure chart. It shows changes over time of the expander rotation speed N2, the opening degree of the low-pressure expander inlet valve 22, and the opening degree of the low-pressure expander bypass valve 27. The time axis of the upper chart corresponds to the time axis of the lower chart.

  As shown in FIGS. 3 and 4, the startup control is roughly divided into four steps: an initial cooling step, an initial startup step, a dangerous speed region passing step, and a rotation speed increasing step. The initial cooling step is performed before starting up the expanders 37 and 38 (that is, before starting the rotation).

(Initial cooling step)
When the rotor shaft rotates in a state where the high-pressure expander 37 and the low-pressure expander 38 and their surroundings are not cooled to the liquid nitrogen temperature, and the rotation speed enters the dangerous speed region, it is caused by the synchronous component of the natural frequency. In addition to the shaft vibration that occurs, unstable vibration caused by an asynchronous component that is not related to the natural frequency also occurs. If the shaft vibration becomes excessive, the bearing may be seized. Therefore, in the initial cooling step, when the entire apparatus of the raw material gas liquefying apparatus 100 is in the normal temperature state before the start-up, the initial apparatus 73 uses the initial cooler 73 (nitrogen line 70) and the entire apparatus has a temperature of about liquid nitrogen. Initial cooling is performed until

  In the initial cooling step, the opening degree of the low-pressure expander bypass valve 27 is lowered from a predetermined circulation opening degree to a predetermined initial starting opening degree. The opening degree of the low-pressure expander bypass valve 27 is maintained at the initial startup opening degree until the rotation speed increase step is started.

  In the initial cooling step, the opening of the high-pressure expander inlet valve 21 is raised to a predetermined initial cooling opening and maintained at the initial cooling opening. The initial cooling opening degree of the high-pressure expander inlet valve 21 is not closed but slightly opened. Therefore, at the initial cooling opening degree of the high-pressure expander inlet valve 21, the refrigerant having a flow rate that does not rotate the high-pressure expander 37 is allowed to flow into the high-pressure expander 37.

  Further, in the initial cooling step, the opening degree of the low-pressure expander inlet valve 22 is increased from the closed state to a predetermined initial cooling opening degree before the expanders 37 and 38 are started (that is, before the rotation is started). When the low-pressure expander inlet valve 22 is at the initial cooling opening degree, it is allowed that a flow amount of refrigerant that does not rotate the low-pressure expander 38 flows into the low-pressure expander 38.

  The control device 6 waits until the opening degree of the low-pressure expander inlet valve 22 reaches the initial cooling opening degree, and starts the initial cooling flow rate control of the low-pressure expander 38. In the initial cooling flow rate control of the low-pressure expander 38, the control device 6 operates the opening degree of the low-pressure expander inlet valve 22 to perform feedback so that the low-pressure expander inlet-side flow rate F2 becomes a predetermined initial cooling flow rate set value. Control. The initial cooling flow rate setting value is a refrigerant flow rate that does not rotate the rotor shaft of the low-pressure expander 38, and may be set to a value that is 80 to 90% or less of the refrigerant flow rate at which the rotor shaft starts to rotate.

  The initial cooling flow rate control of the low-pressure expander 38 is continued until the low-pressure expander outlet temperature T2 reaches a predetermined cooling determination temperature. When the low-pressure expander outlet temperature T2 reaches a predetermined cooling determination temperature, the initial activation flag of the low-pressure expander 38 is turned ON.

(Initial start-up step of the low-pressure expander 38)
When the initial activation flag of the low pressure expander 38 is turned ON, the control device 6 starts an initial activation step of the low pressure expander 38. In the initial startup step of the low-pressure expander 38, schedule control and rotation speed control of the opening degree of the low-pressure expander inlet valve 22 are selectively performed.

  The control device 6 starts counting up when the initial activation flag is ON, and generates a first opening degree command based on a predetermined valve opening degree schedule. Note that the valve opening schedule of the low-pressure expander inlet valve 22 defines the relationship between the time after the start of counting up and the valve opening setting value of the low-pressure expander inlet valve 22. The control device 6 derives a valve opening setting value corresponding to the time from the start of counting up, and generates a first opening command based on the valve opening setting value.

  Further, when the initial activation flag is turned ON, the control device 6 generates a second opening degree command based on the rotational speed control. Specifically, the control device 6 uses the low-pressure expander rotation speed N2 as a control amount, sets a predetermined maximum rotation speed setting value as a target value, sets the opening of the low-pressure expander inlet valve 22 as an operation amount, and sets the control amount as A second opening degree command is generated by feedback control that matches the target value. Here, the maximum rotation speed setting value of the low-pressure expander 38 is a rotation speed smaller than the critical speed region of the low-pressure expander 38. The critical speed region is a rotational speed region inherent to the expanders 37 and 38, and is a rotational speed region including the rotational speed of the rotor shaft at which the turbine resonates and the periphery thereof.

  The control device 6 compares the first opening degree command and the second opening degree instruction, and outputs the smaller one of them as the opening degree instruction to the low pressure expander inlet valve 22. Usually, since the low pressure expander 38 is not rotating at the start of the initial activation step, the low pressure expander inlet valve 22 is operated based on the first opening degree command by the valve opening schedule control, and the low pressure expander inlet valve 22 is operated. When the low-pressure expander 38 starts to rotate with the increase of the opening degree, the low-pressure expander inlet valve 22 is operated based on the second opening degree command based on the rotational speed control. In this manner, the valve opening schedule control is automatically switched to the rotation speed control. Thereby, it is possible to perform the initial activation without entering the dangerous speed region.

(Passing step of dangerous speed region of low-pressure expander 38)
When the low-pressure expander rotational speed N2 is stabilized at the maximum rotational speed setting value, the critical speed region passing flag is turned ON. Note that “the rotational speed is stable” of the expanders 37 and 38 means that a state in which the fluctuation of the rotational speed is equal to or less than a predetermined value continues for a predetermined time.

  When the dangerous speed region passage flag is turned ON, the control device 6 switches the target value from the maximum rotational speed setting value to a predetermined rotational speed setting value before the speed increase, and performs the rotational speed control. Here, the rotational speed setting value before the speed increase is a rotational speed exceeding the dangerous speed region.

  The control device 6 uses the low-pressure expander rotation speed N2 as the control amount, sets the rotation speed setting value before speed increase as the target value, sets the opening of the low-pressure expander inlet valve 22 as the operation amount, and matches the control amount to the target value. An opening degree command is generated by such feedback control and is output to the low-pressure expander inlet valve 22. As a result, the low-pressure expander rotational speed N2 is rapidly increased to the rotational speed setting value before the speed increase, and quickly passes through the dangerous speed region.

  When the low-pressure expander rotational speed N2 is stabilized at the pre-acceleration rotational speed set value and the opening of the low-pressure expander inlet valve 22 is stabilized, the initial activation flag of the high-pressure expander 37 is turned on. During the initial start-up step and the dangerous speed region passing step of the high-pressure expander 37, which will be described later, the control device 6 controls the low-pressure expander inlet so that the low-pressure expander rotation speed N2 maintains the rotation speed setting value before acceleration. The opening degree of the valve 22 is controlled.

(Initial cooling / starting step of the high-pressure expander 37)
When the initial activation flag of the high pressure expander 37 is turned ON, the control device 6 starts an initial cooling / activation step of the high pressure expander 37. The start-up control of the high-pressure expander 37 includes an initial cooling step, an initial start-up step, a dangerous speed region passing step, and a rotation speed increase step, as in the start-up control of the low-pressure expander 38.

  As described above, in the initial cooling step, the high-pressure expander 37 already has a flow rate of refrigerant that does not rotate the rotor shaft. The refrigerant cools the high-pressure expander 37 and its surroundings while the initial startup step and the dangerous speed region passing step of the low-pressure expander 38 are performed.

  In the initial startup step of the high-pressure expander 37, the valve opening schedule control and the rotational speed control are selectively performed in the same manner as the initial startup step of the low-pressure expander 38 described above.

  Specifically, the control device 6 starts counting up with the initial activation flag being turned ON as a trigger, and generates a first opening degree command based on a predetermined valve opening degree schedule. On the other hand, the control apparatus 6 produces | generates a 2nd opening degree command by rotation speed control. In other words, the high pressure expander rotational speed N1 is set as a control amount, a predetermined maximum rotational speed set value is set as a target value, the opening degree of the high pressure expander inlet valve 21 is set as an operation amount, and feedback is performed so that the control amount matches the target value. A second opening degree command is generated by the control. The control device 6 compares the first opening degree command and the second opening degree instruction, and outputs the smaller one of them as the opening degree instruction to the high-pressure expander inlet valve 21. Thereby, it is possible to perform the initial activation without entering the dangerous speed region.

(Dangerous speed region passing step of high-pressure expander 37)
When the high-pressure expander rotational speed N1 is stabilized at the maximum rotational speed, the dangerous speed region passing flag is turned ON. When the dangerous speed region passage flag is turned ON, the control device 6 starts the dangerous speed region passage step. In the critical speed region passing step of the high-pressure expander 37, the target value in the rotational speed control is set from the maximum rotational speed setting value to a predetermined rotational speed before the speed increase similarly to the dangerous speed region passing step of the low-pressure expander 38 described above. Switch to value.

  The control device 6 controls the opening degree of the high-pressure expander inlet valve 21 to perform feedback control so that the high-pressure expander rotation speed N1 becomes the rotation speed before acceleration set value. As a result, the high-pressure expander rotational speed N1 can be rapidly increased to the rotational speed setting value before the speed increase, and can quickly pass through the dangerous speed region.

(Speed increase step)
When the high-pressure expander rotational speed N1 reaches the rotational speed before acceleration setting value, the rotational speed acceleration flag is turned ON. When the rotation speed increase flag is turned ON, the control device 6 starts a rotation speed increase step for the high-pressure expander 37 and the low-pressure expander 38.

  In the rotation speed increasing step, the control device 6 decreases the opening degree of the high-pressure expander bypass valve 24 from the initial startup opening degree to a predetermined steady operation opening degree at a predetermined reduction rate. Similarly, the control device 6 reduces the opening of the low-pressure expander bypass valve 27 at a predetermined decrease rate from the initial startup opening to a predetermined steady operation opening.

  Further, in the rotational speed acceleration step, the control device 6 starts counting up when the rotational speed acceleration flag is turned on, obtains a target value of the rotational speed based on a predetermined rotational speed acceleration schedule, and The opening degree of the inlet valve 21 is operated to perform feedback control so that the high-pressure expander rotational speed N1 matches the target value. As a result, the high-pressure expander rotational speed N1 rises from the pre-acceleration rotational speed setting value to the rated rotational speed of the high-pressure expander 37.

  Similarly, the control device 6 obtains a target value of the rotational speed based on a predetermined rotational speed acceleration schedule, operates the opening of the low-pressure expander inlet valve 22, and sets the low-pressure expander rotational speed N2 as the target value. Feedback control is performed to match. As a result, the low-pressure expander rotational speed N2 rises from the pre-acceleration rotational speed setting value to the rated rotational speed of the low-pressure expander 38.

  Thus, by reducing the opening degree of the high-pressure expander bypass valve 24 and the low-pressure expander bypass valve 27 at a predetermined reduction rate regardless of the rotation speed, the high-pressure expander inlet valve 21 automatically adjusted by the rotation speed control and Interference with a change in the opening of the low-pressure expander inlet valve 22 can be avoided, and over-rotation and rapid ascent of the expanders 37 and 38 can be prevented.

  If the heat exchangers 81 to 86 are rapidly cooled or heated due to a rapid decrease or increase in the refrigerant temperature, for example, plate fins in the heat exchanger may be damaged by heat shock. In order to reduce the load applied to the heat exchangers 81 to 86, the temperature change in the heat exchangers 81 to 86 must be within a predetermined allowable range when the expanders 37 and 38 are started and stopped. Don't be. Therefore, the rotation speed increase schedule of the high-pressure expander 37 sets the rotation speed of the high-pressure expander 37 from the rotation speed setting before the increase while suppressing the temperature change of the heat exchangers 81 to 86 within a predetermined allowable range. The relationship between the time and the rotation speed (target value) of the high-pressure expander 37 that can be increased to the rated rotation speed is defined. Similarly, the rotation speed increase schedule of the low-pressure expander 38 sets the rotation speed of the low-pressure expander 38 from the rotation speed before increase speed while suppressing the temperature change of the heat exchangers 81 to 86 within a predetermined allowable range. The relationship between the time and the rotation speed (target value) of the low-pressure expander 38 is determined so as to increase the rotation speed to the rated rotation speed.

  Then, the control device 6 increases the rotational speed of the high-pressure expander 37 when the high-pressure expander rotational speed N1 is stabilized at the rated rotational speed and the opening degree of the high-pressure expander bypass valve 24 reaches the steady operation opening degree. End the fast step. Similarly, when the low-pressure expander rotational speed N2 is stabilized at the rated rotational speed and the opening degree of the low-pressure expander bypass valve 27 reaches the steady operation opening degree, the control device 6 rotates the rotational speed of the low-pressure expander 38. End the speed up step. The end timings of the rotation speed increase steps of the high-pressure expander 37 and the low-pressure expander 38 are scheduled to be substantially the same according to the respective rotation speed increase schedules. When the rotational speed increasing step of the high-pressure expander 37 and the low-pressure expander 38 is completed, the control device 6 ends the start-up control of the high-pressure expander 37 and the low-pressure expander 38.

(Stop control)
Next, stop control by the control device 6 will be described. FIG. 5 is a diagram illustrating the flow of the stop control process, and FIG. 6 is a timing chart of the stop control. FIG. 5 illustrates the flow of the stop control process for the low-pressure expander 38, but the stop control for the low-pressure expander 38 and the stop control for the high-pressure expander 37 have different schedules and set values used. The content of the process is substantially the same, and the process of the stop control of the high-pressure expander 37 will be described with reference to FIG. In FIG. 6, the upper chart represents the high-speed expander rotation speed N1, the opening degree of the high-pressure expander inlet valve 21, and the opening degree of the high-pressure expander bypass valve 24, and the lower chart represents the low-pressure expander. It shows changes over time in the rotational speed N2, the opening degree of the low-pressure expander inlet valve 22, and the opening degree of the low-pressure expander bypass valve 27. The time axis of the upper chart corresponds to the time axis of the lower chart.

  As shown in FIG. 5 and FIG. 6, when starting the stop control, the control device 6 increases the opening of the high-pressure expander bypass valve 24 from the circulation opening to the stop opening at a predetermined increase rate, and at the same time, the low-pressure expansion The opening of the machine bypass valve 27 is increased from the steady operation opening to the stop opening at a predetermined increase rate.

  When the stop control is started, the control speed reduction flag is turned ON, the control device 6 starts counting up, and obtains a target speed value based on a predetermined speed reduction schedule of the high-pressure expander 37. Then, the control device 6 controls the opening of the high-pressure expander inlet valve 21 to perform feedback control so that the high-pressure expander rotational speed N1 matches the target value. As a result, the high-pressure expander rotational speed N1 is decelerated from the rated rotational speed of the high-pressure expander 37 to a predetermined pre-stop rotational speed. The rotational speed reduction schedule of the high-pressure expander 37 is to reduce the rotational speed of the high-pressure expander 37 from the rated rotational speed to the pre-stop rotational speed while suppressing the temperature change of the heat exchangers 81 to 86 within a predetermined allowable range. The relationship between the time and the rotation speed (target value) of the high-pressure expander 37 is determined.

  Similarly, the control device 6 obtains a target value for the rotational speed based on a predetermined rotational speed reduction schedule for the low-pressure expander 38. Then, the control device 6 operates the opening of the low-pressure expander inlet valve 22 to perform feedback control so that the low-pressure expander rotational speed N2 matches the target value. As a result, the low-pressure expander rotational speed N2 is decelerated from the rated rotational speed of the low-pressure expander 38 to a predetermined pre-stop rotational speed. The rotational speed reduction schedule of the low-pressure expander 38 is to reduce the rotational speed of the low-pressure expander 38 from the rated rotational speed to the pre-stop rotational speed while suppressing the temperature change of the heat exchangers 81 to 86 within a predetermined allowable range. The relationship between the time and the rotational speed (target value) of the low-pressure expander 38 is determined.

  Thus, by reducing the opening degree of the high-pressure expander bypass valve 24 and the low-pressure expander bypass valve 27 at a predetermined increase rate regardless of the rotation speed, the high-pressure expander inlet valve 21 automatically adjusted by the rotation speed control and Interference with the opening degree change of the low-pressure expander inlet valve 22 can be avoided, and over-rotation and sudden deceleration of the expanders 37 and 38 can be prevented.

  When the high-pressure expander rotational speed N1 is stable at the pre-stop rotational speed and the high-pressure expander bypass valve 24 reaches the stop opening, the deceleration of the high-pressure expander 37 stops. When the low-pressure expander rotational speed N2 is stabilized at the pre-stop rotational speed and the low-pressure expander bypass valve 27 reaches the stop opening, the deceleration of the low-pressure expander 38 stops. Then, when both the expanders 37 and 38 are stopped, the rotation speed reduction flag is turned OFF.

  When the rotational speed deceleration flag is turned OFF, the control device 6 outputs a closing degree command to the high-pressure expander inlet valve 21 and the low-pressure expander inlet valve 22. As a result, the high-pressure expander inlet valve 21 is closed, and the high-pressure expander rotational speed N1 is suddenly decelerated to 0 and can pass through the dangerous speed region quickly. Similarly, the low-pressure expander inlet valve 22 is closed, and the low-pressure expander rotational speed N2 is suddenly decelerated to 0, so that the dangerous speed region can be quickly passed. Thus, since the expanders 37 and 38 pass through the dangerous speed region quickly, the expanders 37 and 38 can be stopped while avoiding excessive shaft vibration. After completion of the stop control, the opening of the high pressure expander bypass valve 24 and the low pressure expander bypass valve 27 is increased from the stop opening to the circulation opening at a predetermined increase rate.

  As described above, the raw material gas liquefying apparatus 100 according to the present embodiment has the feed line 1 for supplying the raw material gas whose boiling point is lower than that of the nitrogen gas, and the refrigerant circulation in which the refrigerant for cooling the raw material gas circulates. A refrigerant circulation line that is a line 3 and includes turbine-type expanders 37 and 38 that expand the refrigerant to generate cold heat, and expander inlet valves 21 and 22 provided on the inlet side of the expanders 37 and 38. 3, heat exchangers 81 to 86 that perform heat exchange between the source gas and the refrigerant, a cooler 73 that performs initial cooling of the source gas and the refrigerant by heat exchange with liquid nitrogen, and rotation of the expanders 37 and 38. Expander rotation speed sensors 56 and 57 for detecting the numbers N1 and N2 and a control device 6 for performing operation control on the feed line 1 and the refrigerant circulation line 3 are provided.

  The control device 6 controls the expansion valve inlet valves 21 and 22 by feedback control that makes the rotation speeds N1 and N2 of the expanders 37 and 38 coincide with a predetermined target value when the expanders 37 and 38 are started and stopped. An opening command is generated, and the opening command is output to the expander inlet valves 21 and 22.

  Moreover, the control method of the raw material gas liquefying apparatus 100 according to the present embodiment operates the expanders 37 and 38 by operating the opening degree of the expander inlet valves 21 and 22 when the expanders 37 and 38 are started and stopped. Is characterized in that feedback control is performed so that the rotation speeds N1 and N2 coincide with a predetermined target value.

  In the raw material gas liquefying apparatus 100 and its control method, when the expanders 37 and 38 are started and stopped, not the valve opening degree of the expander inlet valves 21 and 22 but the rotation speed of the expanders 37 and 38 is directly set. Be controlled. Thereby, even when the expanders 37 and 38 are started and stopped, it is possible to control the cold heat generated by the expanders 37 and 38. Further, even if the operating characteristics of the expanders 37 and 38 change, it is possible to prevent the rotational speed of the expanders 37 and 38 from entering the dangerous speed region without a plan when the expanders 37 and 38 are started and stopped. Further, by controlling the rotation speed of the expanders 37 and 38, the dangerous speed region can be quickly passed, and the shaft vibration of the expanders 37 and 38 can be suppressed. As a result, damage due to excessive shaft vibration of the expanders 37 and 38 such as seizure of the bearings of the expanders 37 and 38 can be avoided.

  In addition, in the raw material gas liquefying apparatus 100 and the control method thereof according to the present embodiment, the control apparatus 6 is supplied with the initially cooled refrigerant at a predetermined initial cooling flow rate that does not rotate the expander 37 before the expander 37 is started. An opening command for the expander inlet valve 21 is generated so as to be introduced into the expander 37, and the opening command is output to the expander inlet valve 21.

  As described above, before starting the expanders 37 and 38, the opening of the expander inlet valve 22 is operated to cool the refrigerant so that the refrigerant having the initial cooling flow rate that does not rotate the expander 38 is introduced into the expander 38. By controlling the flow rate, the expander 38 and its surroundings can be cooled without rotating the expander 38. Compared to the case where the shaft seal leakage of the bearing of the expander 38 is used to cool the expander 38 and its surroundings as in Patent Document 1, the flow rate of the refrigerant becomes gentler and the cooling starts. Thus, the time required for starting up the expanders 37 and 38 can be shortened.

  In the above embodiment, the initial cooling flow rate control is performed on the low-pressure expander 38, but the same initial cooling flow rate control may be performed on the high-pressure expander 37.

  Further, in the raw material gas liquefying apparatus 100 and the control method thereof according to the present embodiment, the control device 6 determines the rotation speed of the expanders 37 and 38 when the expanders 37 and 38 are started up. A first opening command of the expander inlet valves 21 and 22 is obtained based on a predetermined valve opening schedule that is increased to a predetermined maximum rotational speed setting value smaller than the target value, and the target value is set as the maximum rotational speed setting value; The second opening degree command of the expander inlet valves 21 and 22 is obtained by feedback control for matching the rotation speed of the expander 37 with the maximum rotation speed setting value, and the first opening degree command and the second opening degree command are obtained. The opening command with the smaller value is output to the expander inlet valves 21 and 22.

  According to the valve opening schedule control as described above, the operating characteristics (rotation start) of the expanders 37 and 38 are caused by aging deterioration of the devices of the expanders 37 and 38 and adhesion of impurities contained in the refrigerant to the turbine bearing. Even if the stop characteristic is changed, the initial start-up of the expanders 37 and 38 can be started. Further, according to the rotational speed control with the maximum rotational speed as a target value, even if the expanders 37 and 38 tend to over-rotate immediately after starting rotation, the rotational speeds of the expanders 37 and 38 are at a dangerous speed at a stretch. Entering the area can be avoided.

  Further, in the raw material gas liquefying apparatus 100 and the control method thereof according to the present embodiment, the expansion is started from the predetermined rotational speed before the speed increase that exceeds the dangerous speed region of the expanders 37 and 38 when the expanders 37 and 38 are started. When the rotational speed of the expander is increased to the rated rotational speed of the expanders 37 and 38, the control device 6 allows the temperature change of the heat exchangers 81 to 86 accompanying the change of the rotational speed of the expanders 37 and 38 to a predetermined allowable value. A target value for the rotational speed control is determined based on a predetermined rotational speed acceleration schedule for increasing the rotational speed of the expanders 37 and 38 while keeping it within the range.

  Similarly, in the raw material gas liquefying apparatus 100 and the control method thereof according to the present embodiment, when the expanders 37 and 38 are stopped, the critical speed range of the expanders 37 and 38 is determined from the rated rotational speed of the expanders 37 and 38. When the rotational speed of the expanders 37 and 38 is lowered to a predetermined rotational speed before stopping exceeding the control number, the control device 6 changes the temperature change of the heat exchangers 81 to 86 accompanying the change in the rotational speed of the expanders 37 and 38. A target value for rotational speed control is determined based on a predetermined rotational speed deceleration schedule for decreasing the rotational speed of the expanders 37 and 38 while keeping it within a predetermined allowable range.

  As described above, the rotational speeds of the high-pressure expander 37 and the low-pressure expander 38 gradually increase (acceleration) according to the rotational speed increase schedule, or gradually decrease (decelerate) according to the rotational speed deceleration schedule, The temperature rise of the heat exchangers 81 to 86 due to the insufficient amount of generated heat of the high pressure expander 37 and the low pressure expander 38 can be suppressed within an allowable range. Thereby, in the heat exchangers 81-86, the damage of the plate fin resulting from a heat shock can be prevented.

  In the raw material gas liquefying apparatus 100 and the control method thereof according to the present embodiment, the expanders 37 and 38 include a high-pressure expander 37 and a low-pressure expander 38 provided on the downstream side of the high-pressure expander 37. The expander inlet valves 21 and 22 include a high-pressure expander inlet valve 21 provided on the inlet side of the high-pressure expander 37 and a low-pressure expander inlet valve 22 provided on the inlet side of the low-pressure expander 38. It is included. Then, after the rotational speed of the low-pressure expander 38 reaches a predetermined rotational speed before the acceleration that exceeds the critical speed region of the low-pressure expander 38, the control device 6 determines that the rotational speed of the high-pressure expander 37 is the high-pressure expansion. After reaching a predetermined speed before the speed increase that exceeds the critical speed range of the machine 37 and the high pressure expander 37 and the low pressure expander 38 have reached their respective speed before the speed increase, the high pressure expander 37 and the low pressure expansion The rotation speeds of the low-pressure expander 38 and the high-pressure expander 37 are controlled so that the rotation speed of the machine 38 is increased from the rotation speed before each speed increase to the respective rated rotation speed.

  In this way, after both the high-pressure expander 37 and the low-pressure expander 38 have reached their respective pre-acceleration rotational speeds that exceed the critical speed range, the rotational speeds of the high-pressure expander 37 and the low-pressure expander 38 are set to their respective ratings. By rotating to the rotational speed, it is possible to reliably prevent the rotational speeds of the high-pressure expander 37 and the low-pressure expander 38 from entering the dangerous speed region unexpectedly. In addition, since the high-pressure expander 37 and the low-pressure expander 38 shift the timing of passing through the critical speed region (that is, the timing at which the rotational speed changes sharply), the shaft vibration is suppressed and more stable start-up control is performed. be able to.

  The preferred embodiments of the present invention have been described above, but the present invention may include modifications in the specific structure and / or function details of the above embodiments without departing from the spirit of the present invention. . The configuration of the raw material gas liquefying apparatus 100 can be changed as follows, for example.

  The raw material gas liquefying apparatus 100 according to the above embodiment includes two expanders 37 and 38. However, these numbers depend on the performance of the expanders 37 and 38 and are not limited to the above embodiment.

  For example, one expander may be used. In this case, the operation of the raw material gas liquefying apparatus 100 is controlled in substantially the same manner as in the above embodiment except that the start control and stop control of the high pressure expander 37 are omitted. For example, three or more expanders may be used. In this case, the operation of the raw material gas liquefying apparatus 100 is substantially the same as that of the above embodiment except that the same control as the start control and stop control of the high pressure expander 37 is added for the expanded expander. Is controlled.

  Further, in the raw material gas liquefying apparatus 100 according to the above embodiment, the initial start step and the dangerous speed region passing step of the low pressure expander 38 are performed, and then the initial start step and the dangerous speed region passing step of the high pressure expander 37 are performed. However, the order of the former may be changed, and the latter may be performed first and the former performed later. In this case, before the initial startup step of the high-pressure expander 37, the control device 6 is configured so that the initially cooled refrigerant having a predetermined initial cooling flow rate that does not rotate the high-pressure expander 37 is introduced into the high-pressure expander 37. An opening command for the high-pressure expander inlet valve 21 is generated, and the opening command is output to the high-pressure expander inlet valve 21.

  In addition, the raw material gas liquefying apparatus 100 according to the above embodiment includes two compressors 32 and 33 and six heat exchangers 81 to 86. However, these numbers depend on the performance of the compressors 32 and 33 and the heat exchangers 81 to 86, and are not limited to the above embodiment.

1: Feed line 3: Refrigerant circulation line 6: Control device 16: Supply system Joule-Thomson valve 20: Liquefier 21: High pressure expander inlet valve 22: Low pressure expander inlet valve 23: High pressure expander bypass flow path 24: High pressure expansion Machine bypass valve 26: Low pressure expander bypass flow path 27: Low pressure expander bypass valve 31C: Cold heat generation flow path 32: Low pressure compressor 33: High pressure compressor 36: Circulation system Joule-Thomson valve 37: High pressure expander 38: Low pressure expansion Machine 40: Liquefied refrigerant storage tank 41: Refrigerant liquefaction route 42: Cold heat generation route 51: High pressure expander outlet temperature sensor 52: Low pressure expander outlet temperature sensor 56: High pressure expander rotation speed sensor 57: Low pressure expander rotation speed sensor 58: High pressure expander inlet side flow rate sensor 59: Low pressure expander inlet side flow rate sensor 61: Start control unit 62: Stop control unit 70: Nitrogen line 71 Liquid nitrogen storage tank 73: Initial condenser 81 to 86: heat exchanger 88: condenser 100: raw material gas liquefaction apparatus

Claims (12)

  1. A feed line for supplying a raw material gas whose boiling point is lower than that of nitrogen gas;
    A refrigerant circulation line through which a refrigerant for cooling the raw material gas circulates, and expands the refrigerant to generate cold heat, and an expander inlet provided on the inlet side of the expander A refrigerant circulation line having a valve;
    A heat exchanger in which heat exchange is performed between the source gas and the refrigerant;
    A cooler that performs initial cooling of the source gas and the refrigerant by heat exchange with liquid nitrogen;
    An expander rotation speed sensor for detecting the rotation speed of the expander;
    When the expander is started and stopped, an opening degree command for the expander inlet valve is generated by feedback control that matches the rotation speed of the expander with a predetermined target value. A control device for outputting to the valve,
    Raw material gas liquefaction equipment.
  2. The controller opens the expander inlet valve so that the initially cooled refrigerant having a predetermined initial cooling flow rate that does not rotate the expander is introduced into the expander before the expander is started. A degree command is generated and the opening degree command is output to the expander inlet valve.
    The raw material gas liquefying apparatus according to claim 1.
  3. When the control device starts the expander,
    Based on a predetermined valve opening schedule for increasing the rotation speed of the expander to a predetermined maximum rotation speed setting value smaller than the critical speed region of the expander, a first opening command of the expander inlet valve is issued. Seeking
    The target value is set as the maximum rotation speed setting value, and a second opening degree command of the expander inlet valve is obtained by feedback control for matching the rotation speed of the expander with the maximum rotation speed setting value,
    A smaller opening command of the first opening command and the second opening command is output to the expander inlet valve;
    The raw material gas liquefying apparatus according to claim 1 or 2.
  4. At the time of starting the expander, when increasing the rotation speed of the expander from a predetermined rotation speed before the speed increase exceeding the critical speed range of the expander to the rated rotation speed of the expander,
    The control device is based on a predetermined rotational speed acceleration schedule for increasing the rotational speed of the expander while suppressing a temperature change of the heat exchanger accompanying a change in the rotational speed of the expander within a predetermined allowable range. Determining the target value;
    The raw material gas liquefying apparatus as described in any one of Claims 1-3.
  5. When the expander is stopped, and when the rotational speed of the expander is decreased from the rated rotational speed of the expander to a predetermined pre-stop rotational speed that exceeds the dangerous speed range of the expander,
    The control device is based on a predetermined rotational speed reduction schedule for decreasing the rotational speed of the expander while suppressing a temperature change of the heat exchanger accompanying a change in the rotational speed of the expander within a predetermined allowable range. Determining the target value;
    The raw material gas liquefying apparatus according to any one of claims 1 to 4.
  6. The expander includes a high-pressure expander and a low-pressure expander provided on the downstream side of the high-pressure expander,
    The expander inlet valve includes a high-pressure expander inlet valve provided on the inlet side of the high-pressure expander, and a low-pressure expander inlet valve provided on the inlet side of the low-pressure expander,
    The control device may be configured such that the rotation speed of the high-pressure expander increases the risk of the high-pressure expander after the rotation speed of the low-pressure expander reaches a predetermined rotation speed before the acceleration that exceeds the dangerous speed range of the low-pressure expander. After reaching a predetermined rotational speed before the acceleration exceeding the speed region, and both the high-pressure expander and the low-pressure expander have reached their rotational speed before the acceleration, the high-pressure expander and the low-pressure expander Controlling the rotational speeds of the low-pressure expander and the high-pressure expander so as to increase the rotational speed from the rotational speed before the speed increase to the rated rotational speed of the respective persons.
    The raw material gas liquefying apparatus according to any one of claims 1 to 5.
  7. A feed line for supplying a raw material gas whose boiling point is lower than that of nitrogen gas;
    A refrigerant circulation line through which a refrigerant for cooling the raw material gas circulates, and expands the refrigerant to generate cold heat, and an expander inlet provided on the inlet side of the expander A refrigerant circulation line having a valve;
    A heat exchanger in which heat exchange is performed between the source gas and the refrigerant;
    A cooler that performs initial cooling of the source gas and the refrigerant by heat exchange with liquid nitrogen;
    A control method of a raw material gas liquefying device comprising a control device for performing operation control on the feed line and the refrigerant circulation line,
    At the time of starting and stopping of the expander, the opening degree of the expander inlet valve is operated, and feedback control is performed so that the rotation speed of the expander matches a predetermined target value.
    Control method of raw material gas liquefying apparatus.
  8. Before starting the expander, the opening degree of the expander inlet valve is manipulated so that the initially cooled refrigerant having a predetermined initial cooling flow rate that does not rotate the expander is introduced into the expander. Controlling the flow rate introduced into the expander to the initial cooling flow rate,
    The control method of the raw material gas liquefying apparatus according to claim 7.
  9. At startup of the expander,
    A first opening command of the expander inlet valve based on a predetermined valve opening schedule for increasing the rotation speed of the expander to a predetermined maximum rotation speed setting value smaller than a critical speed region of the expander; Of the second opening command of the expander inlet valve based on feedback control for setting the target value as the maximum rotational speed setting value and making the rotational speed of the expander coincide with the target value, open the smaller one of the values. Operating the opening of the expander inlet valve based on the degree command,
    The control method of the raw material gas liquefying apparatus according to claim 7 or 8.
  10. At the time of starting the expander, when the rotation speed of the expander is increased from a predetermined rotation speed before a speed increase exceeding a critical speed range of the expander to a rated rotation speed of the expander, the expander The target value is obtained based on a predetermined rotational speed acceleration schedule for increasing the rotational speed of the expander while suppressing the temperature change of the heat exchanger with a change in the rotational speed of
    The control method of the raw material gas liquefying apparatus as described in any one of Claims 7-9.
  11. At the time of stopping the expander, when the rotational speed of the expander is decreased from the rated rotational speed of the expander to a predetermined pre-stop rotational speed that exceeds the critical speed range of the expander, Obtaining the target value based on a predetermined rotation speed reduction schedule for lowering the rotation speed while suppressing a temperature change of the heat exchanger accompanying a change in the rotation speed within a predetermined allowable range;
    The control method of the raw material gas liquefying apparatus as described in any one of Claims 7-10.
  12. The expander includes a high-pressure expander and a low-pressure expander provided on the downstream side of the high-pressure expander,
    The expander inlet valve includes a high-pressure expander inlet valve provided on the inlet side of the high-pressure expander, and a low-pressure expander inlet valve provided on the inlet side of the low-pressure expander,
    The predetermined number of revolutions of the high-pressure expander exceeds the critical speed range of the high-pressure expander after the number of revolutions of the low-pressure expander reaches a predetermined number of revolutions before the acceleration that exceeds the critical speed range of the low-pressure expander. And the high-pressure expander and the low-pressure expander both reach their respective rotation speeds before the speed increase, and then the rotation speeds of the high-pressure expander and the low-pressure expander are set to their respective rotation speeds. Controlling the rotational speed of the low-pressure expander and the high-pressure expander so as to increase from the rotational speed before the speed increase to the rated rotational speed of each
    The control method of the raw material gas liquefying apparatus as described in any one of Claims 7-11.
JP2016238535A 2016-12-08 2016-12-08 Material gas liquefaction device and its control method Pending JP2018096556A (en)

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JP2016238535A JP2018096556A (en) 2016-12-08 2016-12-08 Material gas liquefaction device and its control method
PCT/JP2017/043510 WO2018105565A1 (en) 2016-12-08 2017-12-04 Raw material gas liquefaction device and control method for same
US16/465,430 US20200003070A1 (en) 2016-12-08 2017-12-04 Raw material gas liquefying device and method of controlling this raw material gas liquefying device
AU2017373438A AU2017373438B2 (en) 2016-12-08 2017-12-04 Raw material gas liquefying device and method of controlling this raw material gas liquefying device
EP17878280.1A EP3553436A4 (en) 2016-12-08 2017-12-04 Raw material gas liquefaction device and control method for same
CN201780056417.1A CN109690216A (en) 2016-12-08 2017-12-04 Unstrpped gas liquefying plant and its control method

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JPH0718611B2 (en) * 1986-11-25 1995-03-06 株式会社日立製作所 Weight reduction operation method of cryogenic liquefaction refrigeration system
JPH01102289A (en) * 1987-10-16 1989-04-19 Kobe Steel Ltd Helium liquefying refrigerator
JPH01269875A (en) * 1988-04-22 1989-10-27 Hitachi Ltd Liquefaction control method and device for liquefying and refrigerating equipment
JPH08285395A (en) * 1995-04-10 1996-11-01 Kobe Steel Ltd Device for liquefying herium
FR2999693B1 (en) * 2012-12-18 2015-06-19 Air Liquide Refrigeration and / or liquefaction device and corresponding method
JP6591185B2 (en) * 2015-03-26 2019-10-16 川崎重工業株式会社 Method for starting and stopping raw material gas liquefier, and raw material gas liquefying device

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EP3553436A1 (en) 2019-10-16
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EP3553436A4 (en) 2020-08-05
AU2017373438B2 (en) 2020-05-14

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